1. Field of the Invention
The present invention relates to a surrounding surveillance system for surveillance of surroundings of a mobile body, such as a vehicle for transporting persons or things, and a mobile body carrying the same.
2. Description of the Related Art
A recent increase in traffic accidents raises a significant public concern. Particularly, accidents caused by a pedestrian walking against traffic, angle crash of vehicles, rear-end crash of vehicles and the like frequently occur at intersections, such as Y-junction, crossroad and the like. A cause of traffic accidents occurring at such intersections is considered to be that both vehicle drivers and pedestrians have a narrow view compared to that required for confirmation of safety. As a result, drivers and pedestrians cannot pay sufficient attention to their surroundings, so that they cannot recognize danger quickly. Therefore, there is a keen demand for improvement of vehicles, arousal of driver's attention, improvement of roadway environment, and the like.
Conventionally, a traffic mirror is placed at an intersection, such as Y-junction, crossroad or the like, which obstructs a view, in order to improve the roadway environment. However, the view is still narrow in spite of the mirror, and the number of mirrors is not yet sufficient. Thus, safety measures are not sufficient.
To achieve the safety of a vehicle (particularly, to look behind for traffic), for example, a surveillance camera is provided at the rear portion of the vehicle and an image taken by the surveillance camera is displayed on a monitor placed at a side of a driver's seat or a dashboard (the camera and the monitor are connected via a cable). Such a system is widely used in large-size vehicles, such as buses and the like, and a portion of passenger vehicles. In this case, however, to assure safety in the lateral directions of the vehicle mostly relies on the vehicle driver's vision. Recognition of danger is frequently delayed at a place, such as an intersection, which obstructs the driver's view.
The above-described surveillance camera generally has a narrow vision. One such camera can be used to determine the presence or absence of an obstacle or the risk of collision with another object in one direction, but not in a wide range. In order to determine the presence or absence of an obstacle or the risk of collision with another object in a wide range, the angle of the camera needs to be changed, for example.
For example, Japanese Laid-Open Publication No. 2002-218451 discloses a method of displaying an image (overhead view) of a visual field oriented 90 degrees downward (downward along a vertical axis) using an omnidirectional vision sensor comprising an optical system capable of obtaining an image of a 360-degree visual field and capable of accurate central projection transformation of the image, and an imaging section for converting the optical image obtained by the optical system to image data. In this conventional technology, the omnidirectional vision sensor is provided on a bumper or an outside rearview mirror of a vehicle. Alternatively, for example, Japanese Laid-Open Publication No. 2003-125396 discloses a vehicle surrounding surveillance apparatus in which the omnidirectional vision sensor is incorporated into an outside rearview mirror of a vehicle.
When using a vehicle, the driver often encounters situations which should be handled while confirming safety. For example, the driver has to not only look forward when driving a vehicle, but also look at surroundings of the vehicle when starting it, and look at the right, left and rear directions of the vehicle when turning right or left or going in or out of a parking lot or a garage. Although it is very important for the driver to look and confirm the safety in these manners, the structure of a vehicle makes it difficult and troublesome for the driver to confirm the safety of a blind spot which cannot be viewed from the driver's seat.
In order to check a 360-degree area around a vehicle using the conventional surveillance camera, the driver of the vehicle needs to change the angle of the camera, which outputs an image to a monitor, depending on the current situation. Such manipulation is significantly troublesome for vehicle drivers.
In the surrounding surveillance apparatuses of Japanese Laid-Open Publication No. 2002-218451 and Japanese Laid-Open Publication No. 2003-125396, a single omnidirectional vision sensor can be used to obtain a 360-degree image around a vehicle. However, since the optical axis of the omnidirectional vision sensor is oriented along an axis normal to the ground, an area which is immediately below the omnidirectional vision sensor and near the vehicle is a blind spot due to the omnidirectional vision sensor itself. Therefore, such an area is a blind spot even if the omnidirectional vision sensor is provided on, or incorporated into, an outside rearview mirror. In this case, it is not possible to confirm the safety sufficiently.
The above-described techniques provide an image which is an overhead view or a bird's eye view obtained by projecting surrounding objects onto a projection plane (e.g., a road surface). Therefore, the image of a place at a distance from the center of a visual field is significantly distorted, so that such an image is observed by the vehicle driver with a sense of difficulty.